132 PRACTICAL ORGANIC AND BIO-CHEMISTRY 



Properties and Reactions. 



Urea is a white solid which crystallises from water in long prisms 



(Fig. 23). It melts at 132 and is 

 easily soluble in water, alcohol, 

 acetone, but not in ether or chloro- 

 form. 



(i) As an amide it is a weak 

 base and forms salts with strong 

 acids. 



(a) Urea nitrate. If a few cry- 

 stals of urea be dissolved in water 

 on a watch glass and one or two 

 drops of concentrated nitric acid 

 be added, crystals of urea nitrate 

 are 'formed. These are seen to 



FIG 23. Urea. (After Funke.) consist of rhombic six-sided plate- 



lets, often imbricated (like tiles) when examined under the microscope 



(Fig. 24). 



CO(NH.J 2 + HNO 3 = CO(NH 2 ) 2 . HNO 3 . 



() Urea oxalate. If a saturated solution of oxalic acid be used 

 instead of nitric acid, crystals of urea oxalate are formed. Under the 

 microscope they are seen to consist of short rhombic prisms (Fig. 25). 



COOH COOH 



n 



FIG. 24. Urea nitrate. FIG. 25. Urea oxalate. 



(After Funke.) 





